Slide 1

RAM

Chapter 3

Overview

•In this chapter, you will learn how to

–Identify the different types of RAM packaging

–Explain the varieties of DRAM

–Install RAM properly

–Perform basic RAM troubleshooting

DRAM

Program Execution

•Program code is copied from your harddisk into RAM before it is executed…

DRAM

•DRAM (Dynamic Random AccessMemory) is the most popular type ofelectronic memory

–Special type ofsemiconductor thatstores individual 1’sand 0’s usingmicroscopic capacitorsand transistors

Organizing DRAM

•DRAM is considered as the standardRAM due to its low cost, high speed,and ability to store data in a relativelysmall package

•The RAM stores programs and data in8-bit (1-byte) chunks of memory

•DRAM chips are always referenced withrespect to their depth and width

–1 Meg x 4

–256 K x 1

Organizing DRAM

•The depth and width are measured inunits of bits

•They can only be differentiated usingthe information printed on the chipitself

•The physical size and the internalorganization of the chip are not directlycorrelated

Byte Size RAM

Multiple Rows of RAM

Location of DRAM

•The Northbridge knows the real location of theDRAM

RAM Sticks

DIPP (Dual Inline PinPackages)

•The firstgeneration DRAMchips used DIPPs

–Two rows of pinsextending from eitherside of the package

–Very delicate, makingthe installationprocess difficult

30-pin SIPP (SingleInline Pin Package)

•SIPP is a type of package where theRAM is soldered to a small board thatcan be inserted in to the motherboard

–Made RAM installation and removal much simpler

–Plugged directly into the motherboard through aspecial socket

–Easy to install but are delicate

30-pin SIMM (SingleInline MemoryModules)

•SIMMs are physically similar to SIPPs,but have no pins

–Inserted into special SIMM sockets

–Always 8 data bits (1 byte) wide

–All nonparity 30-pin SIMMs have an even numberof chips

–The type of motherboard would indicate whetherparity or nonparity chips are needed

Different Chip Layoutson a SIMM

SIMM Chips and Parity

•When purchasing SIMM chips the questionis whether you need parity or not

•You could get a clue from the chipsalready in the PC – an even (nonparity) orodd (parity) number of chips

•Some PCs let youturn parity off soyou could mixand match

Speed

•The system clockcontrols the CPU speed

•The earlier types of RAMwere called Fast PageMode (FPM) RAM

•Access speed (innanoseconds) refers tothe time taken by theFPM DRAM chip tosupply the chipset withthe requested data

•Each motherboardrequired a certain speed

Talking the Talk

•Each SIMM is called a stick

•Never say 30-pin SIMM or ask for parity ornonparity. Instead say “by 3” or “by 8” or “by9”. These are the most common widths

–X8 is nonparity

–X9 is parity

–X3 is a x9 in a 3-chip package

•Three common sizes are 256KB, 1 MB, 4MB – soask for a “4x8” or “1x3”

•Never give speed in nanoseconds – say I’d likesome 50’s

“I’d like 16 sticks of 1x8 sixties, and four

sticks of 256x9 eighties.”

Banking

•Combining the widths of DRAM to matchthe width of the external data bus iscalled banking

•The number of SIMMs that make up abank depends on the chipset, which inturn depends on the CPU’s external databus size

Banking

•The most important banking rule is thatall SIMMs in the same bank must beidentical

•The connectors where the bank isinstalled are also collectively called abank

Banking

•A bank without any SIMMs is called anunpopulated bank, and a bank filled withSIMMs is called a populated bank

•A bank must be either completelypopulated or completely unpopulated

•This formula can be used to determinethe number of sticks needed to make abank – One bank = Width of the CPU’sexternal data bus ÷ Width of theSIMM/DIMM

–It takes four 30 pin slots in a 486 to makea bank

72-pin SIMMs

•Modern CPUs have 64-bit external databuses and do not use the 30-pin SIMMs

–72-pin SIMMs are an inch longer than 30-pinSIMMs, and have a notch in the middle

–Each 72-pin SIMM is 32-bits wide

–The term “X 32” describes nonparity SIMM and “X36” describes parity SIMM

Four 72-pin SIMMSlots

72-pin SIMMs

•A label can be used for identifyingbetween a parity and nonparity 72-pinSIMM

•Types of parity SIMMs

–True (parity bit for every 8 bits)

–TTL (emulates parity and costs less)

SIMM Sizes and Talk

•1x32 = 4MB, no parity

•1x36 = 4MB, parity

•2x32 = 8MB, no parity

•2x36 = 8MB, parity

•Thru 4, 8, 16 x 32(or 36)

•All x32’s are nonparity – all x36’s areparity

•The size is figured like this: 2x32 means2MB of 32-bits, or 8MB of 8-bits(size=8MB)

“I’d like 4 sticks of 4x32 fifties”

DIMM (Dual InlineMemory Module)

•The 168-pin DIMM is the most popularDRAM package in use today

–Extra pins to handle functions such as bufferingand ECC

–144-pin SO-DIMMs (Small Outline) are used inlaptops

•How many 30-pin SIMMs are needed to make abank on a 486?

–A 486 has a 32-bit external data bus

–30-pin SIMMs are 8 bits wide

–We need four (32 ÷ 8) 30-pin SIMMS per bank

•How many 168-pin DIMMs are need to make abank on a Pentium III?

–A Pentium III has a 64-bit external data bus

–168-bit DIMMS are 64 bits wide

–We need one (64 ÷ 64) DIMM per bank

The Magic BankingFormula

One bank = width of the CPU’s external bus ÷width of the SIMM or DIMM

30-pin SIMMS

8 bits wide

72-pin SIMMS

32 bits wide

168-pin DIMMs

64 bits wide

Summary

CPUs, External Data Bus, and Address bus Sizes

CPU

External Data Bus Bits

Address Bus Bits

Intel 8086

Intel 8088

Intel 80286

Intel 80386DX

Intel 80386SX

AMD AM386DX

AMD AM386SX

Intel 80486DX

AMD AM486DX

Intel Pentium

AMD Athlon

AMD Duron

Intel Pentium Pro

Intel Pentium II

Intel Pentium III

Improvements in DRAMTechnology

EDO DRAM

•EDO (Extended Data Out) is a type ofDRAM that provides the system quickeraccess to data

–Looks exactly like the regular DRAM, so youshould label it

–To take advantage of the EDO, the chipset mustbe designed to handle it

–Now considered obsolete

SDRAM

•SDRAM (Synchronous Dynamic RandomAccess RAM) are tied to the systemclocks

–Faster than DRAMs

–Only available on DIMMs

–Use clock speed instead of access speed

–SDRAM is always a DIMM, but a DIMM isn’talways SDRAM

PC100/133 Standards

•The PC100 and 133 standards define theconstruction of a high-speed DRAM

–Require the use of DIMMs or SO-DIMMs, and aunique chip called the serial presence detect (SPD)to be installed on every DIMM stick

–The SPD provides the system with all the details ofDIMM

ECC

•ECC (Error Correction Code) is a specialtype of RAM used by high-end systems

–Major advance in error checking on DRAM

–RAM sticks of any size can use the ECC DRAM, butit is most common as 168-pin DIMMs

–A motherboard should be designed to use ECC, totake advantage of the ECC RAM

RDRAM

•RDRAM (Rambus DRAM) is a new typeof RAM

–Speeds of up to 800 MHz

–Comes on sticks called RIMMs

–184-pin for desktops and 160-pin SO-RIMM forlaptops

–All slots must be populated - unused slots musthave a CRIMM (Continuity RIMM)

DDR SDRAM (DoubleData Rate)

•DDR SDRAM (Double Data Rate SDRAM)doubles the throughput of SDRAM

–184-pin DIMM packages

–Speed of 200 or 266 MH.

–Used in lower-end systems

Dual-Channel Architecture

•Dual-channel architectures use twosticks of RAM together to increasethroughput

•Double-sided SIMMs/DIMMs

–Double-side sticks have chips on both sides

Installing RAM

Do You Need RAM?

•Two symptoms point to needing moreRAM

–General system sluggishness

–Disk thrashing or excessive hard drive accessing

Mixing DRAM Packages

•Modern motherboards have beendesigned with slots for more than onetype of DRAM

•The motherboard jumper may have to bemoved to enable two different types ofDRAMs to work together

•Most current motherboards have onlyDIMM slots

Speed

•Mixing DRAM speeds can cause thesystem to lock up every few seconds,leading to data corruption

•Experimenting won’t harm anything butthe data

•You can use faster DRAM than themotherboard recommends but won’t seean increase in performance

•You can put different speeds of DRAM indifferent banks as long as they are bothfaster than the speed specified

Banks

•All systems number their banks, usuallystarting at zero

•All banks do not take all sizes of DRAM

•Some systems require you to populatebank 0 first…most systems don’t care

Installing SIMMs

•A notch on one sidewill prevent you frominstalling itincorrectly

•Insert on an angle,then rotate up andsnap into place

What is wrong?

Installing DIMMs

•Swing the side tabs away from upright

•Push the DIMM down somewhat hard –the two tabs should move back intoplace

Installing SO-DIMMs inLaptops

•Remove the panel orlift the keyboard

•Slide the pins intoposition, snap the SO-DIMM down into theretaining clips

•Make sure the systemis off

–No AC connection

–Remove all batteries

Check the RAM

•A halt before the RAM check couldindicate improperly installed RAM

Troubleshooting RAM

•Parity errors, ECC error messages,system lockups, and page faults are afew types of memory errors

•Real and phantom are the two types ofparity errors

–If you get the error “Parity error at xxxxx”, writedown the address – a real parity error will occur atthe same place in memory and indicates a bad RAMstick

•Real errors are errors that the chipsetsdetect from the parity chip